DM5806 datasheet(17/64 Pages) ETC

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1-5

P4 — Interrupt Source Select (Factory Setting: EXT)

This header connector, shown in Figure 1-4, lets you connect one of six interrupt sources for interrupt genera-

tion. These sources are: OT0, OT1, and OT2, which are the three 8254 timer/counter outputs; PC3, which is the

INTRA signal from the 8255 PPI; PC0, which is the INTRB signal from the 8255 PPI; and EXT, an external

interrupt you can route onto the board through the P2 I/O connector. To connect an interrupt source, place the

jumper across the desired set of pins. Note that only ONE interrupt source can be activated at a time.

Fig. 1-4 — Interrupt Source Select Jumper, P4

P5 — 8254 Timer/Counter Clock Sources (Factory Settings: CLK0-OSC, CLK1-OT0, CLK2-OT1)

This header connector, shown in Figure 1-5, lets you select the clock sources for the 8254 timer/counters, TC0,

TC1, and TC2. The factory setting cascades all three timer/counters, with the clock source for TC0 being the on-

board 8 MHz oscillator, the output of TC0 providing the clock for TC1, and the output of TC1 providing the clock

for TC2. You can connect any or all of the sources to an external clock input through the P6 on-board I/O connector,

or you can set TC1 and TC2 to be clocked by the 8 MHz oscillator. Figure 1-6 shows a block diagram of the timer/

counter circuitry to help you with these connections.

NOTE: When installing jumpers on this header, make sure that only one jumper is installed in each group of

two or three CLK pins.

OSC

EC0

OT0

OSC

EC1

OT1

OSC

EC2

Fig. 1-5 — 8254 Timer/Counter Clock Source Jumpers, P5

DM5806 Datasheet(PDF) 17 Page - List of Unclassifed Manufacturers